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Winter is a difficult time for insects |
Winter is quite a difficult time for pollinators. It is cold
and often rainy and the first frosts will wipe out most of the flowers, and
thus drastically reduce the availability of food. Pollinators have evolved various
strategies to overcome this problem. In the following, we describe some of these
strategies.
Bumblebees, at
least from our perspective, have evolved quite a radical way to deal with the
problem. The whole colony including the workers and the old queen die before
winter and only the
young queens reared in the colony will survive to start new
colonies in the following spring. In autumn, they drink a huge amount of nectar
to fill their honey stomach and to build up body fat and then they go searching
for a suitable hiding place for hibernation. These hiding places are mostly
underground, under tree roots and hedgerows or at the base of walls. If the
young queens have not reached a certain weight before the onset of winter they are
likely not to survive winter. Therefore it is really important they find enough
nectar-rich flowers in autumn such as Cosmos (
Cosmos spp.), Michaelmas daisies (
Aster spp.) and single-flowered Dahlias (
Dahlia x hybrida).
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Bumblebee queens need to drink a lot of nectar in autumn |
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A Buff-tailed Bumblebee queen searching for nectar |
In spring, the queens emerge from hibernation and feed on
early flowers such as soft fruit blossom (e.g. Gooseberry and Black currant), early flowering fruit trees, Lesser celandine (
Ficaria verna), Dandelion (
Taraxacum sp.) and spring bulbs (e.g. Crocus) before starting to build new colonies.
The earliest queens to emerge are those of the Buff-tailed Bumblebee (
Bombus terrestris), and you can usually see
them searching for flowers on the first warm days in March. They are quite big
and often a bit clumsy after their long hibernation, and thus easy to spot. The
aptly named Early Bumblebee (
Bombus
pratorum) is the earliest among the UK’s bumblebee species to establish
colonies and the first worker bumblebees you see flying in spring are likely to
be of this species.
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Winter-active Buff-tailed Bumblebee collecting pollen in January |
One exception to the rule is the Buff-tailed Bumblebee,
Bombus terrestris, which can maintain
winter colonies in urban and sub-urban habitats with a good supply of
winter-flowering shrubs such as
Mahonia (
Mahonia spp.), strawberry tree (
Arbutus unedo) and winter heathers (
Erica spp.). So if you see bumblebees flying
around in your garden in December don`t be surprised: you have a
Buff-tailed Bumblebee winter colony somewhere in the vicinity.
Solitary bees do not
maintain colonies and have neither queens nor workers, and therefore they have
evolved different strategies to survive winter. Adult bees are normally active
for only about 3 month in the year (mostly spring/summer depending on the species)
and then die after the business of mating and nest building is finished. The
offspring survives winter either as young adults (most of the early-emerging
bee species), as pupae (many of the later-emerging bees) or as larvae (usually
found among species emerging very late) inside the nest cells which, depending
on the exact species, have been built in hollow reeds, in holes in wood or
walls, in dead stems or in underground chambers.
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Solitary bees have evolved different strategies to survive winter |
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Red mason bee emerging from nesting chamber in spring |
For example, the adults of the common
Red mason bee (Osmia bicornis) emerge early and are active
between March and June. They build their nests in hollow stems, in walls or in holes
in wood and readily use
‘bee-hotels’.
The larvae pupate in late summer and after emergence from the pupal stage the
young adults spend autumn and winter in an unanimated state inside their nest
cells, ready to emerge in spring.
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Mason Bee nesting chambers (closed with mud) in cardboard tubes |
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Red mason bee female building a nest in a 'bee hotel' |
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Ivy bee emerging from an underground nest |
Another example is the
Ivy Bee (Colletes hederae). Adults of this bee species emerge, often in
great numbers, very late in the year (late August/September), around the time
when
Ivy (Hedera spp.), their main
food plant, is starting to flower. They build underground nesting chambers in
south facing, loose, and often sandy soil. In this species, individuals
overwinter as young larvae which will grow on and pupate in the next year.
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Honeybees stop foraging if temperature falls below 10 °C |
Honeybees differ
from bumblebees in as far as they are overwintering as a whole colony inside a
beehive. When the temperature drops below 10
°C, they stop foraging and begin
to cluster around the queen in the central area of the hive. To protect the
queen from the cold winter temperatures outside, the workers, by means of
shivering, keep, the temperature in the center of the cluster at around 27
°C which
is raised even further to 37
°C later on when the queen resumes egg-laying.
The workers work in ‘shifts’ on the outside of the cluster and periodically
have time inside the cluster where they do not exactly rest but are nonetheless
able to enjoy a bit of warmth themselves. Honeybees consume their stored honey
throughout winter in order to be able to produce the body heat required to
maintain the temperature in the cluster.
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This Eristalis sp. hoverfly has overwintered as an adult |
Hoverflies have
two strategies to survive winter. They either hide in the soil as fully-grown
larvae or they hibernate as adults in sheltered places such as the nooks and
crannies of old trees. Hoverflies overwintering as adults are the ones you see
flying around on the first warm days in spring, searching for aphid-infested
plants to lay their eggs on, as the larvae of most hoverflies are voracious consumers
of aphids. Later on in the season, they are joined by the newly emerged
hoverflies of those species that overwinter as larvae.
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Hoverfly enjoying the last warm days in autumn |
Butterflies and
moths display a wide range of
strategies to survive winter. Depending on the species, they can overwinter as
egg, as caterpillar (= the larva of moths and butterflies), as chrysalis (= the
pupa of moths and butterflies), as hibernating imago (= the adult moth or
butterfly), as active imago, or by migration to warmer climates.
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Butterflies and moth survive winter in many different ways |
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Meadow Brown butterflies overwinter as caterpillars |
More moth species
than butterfly species overwinter as egg, but to name just one example of a
butterfly species to overwinter as egg stage, the Silver-washed Fritillary is one
such species. Among butterflies, a much more common strategy for overwintering is
to overwinter as caterpillar. Caterpillars often hibernate among the vegetation,
in seed pods, in silken nests, and in rolled-up leaves, and the caterpillars of
some species will resume feeding during mild spells. In most such species, caterpillars
spend winter as individuals, but in some species they are aggregated into
groups. Small Copper, Meadow Brown and Speckled Wood are all examples of
butterfly species overwintering as caterpillar, with the latter species also
being able to overwinter as pupae.
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This Small copper has overwintered as caterpillar |
By contrast, hawk moths overwinter as pupae
and spend winter in warm cocoons underground. Orange Tip, Holly Blue and Large
and Small White butterflies (with the latter two species sometimes referred to
as ‘Cabbage Whites’) are examples of butterflies overwintering as pupae.
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Hawk moth caterpillars look for suitable overwintering sites in late summer |
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Small Tortoiseshell`s hibernate in sheltered places |
Other butterflies such as Small Tortoiseshell, Peacock, Brimstone
and Comma survive winter as adults and hibernate in sheltered places such as
holes in trees, behind loose bark and in man-made structures such as cellars.
If you come across a hibernating butterfly in your house leave it be if it is
in a cool and undisturbed place (for example your cellar or an unheated spare
room). Try to relocate any disturbed butterflies to a suitable location that is
frost-free and undisturbed, but please do not chuck the butterfly out of your
house if it is freezing outside, as it then is surely going to die.
In a minority of moth and butterfly species, the adults
remain active during winter. These species have evolved the capability to
produce an anti-freezing agent which stops ice-crystals forming in their ‘blood’
if temperatures are below 0 °C (without such an anti-freezing agent,
exposure to subzero temperatures is a sure way to kill an insect). Examples of
such species include the aptly named Winter Moth, which is active between
November and February and which is a pest of fruit trees and the December Moth
which you can encounter even on very cold days, usually in November and
December.
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Painted Ladies migrate back to Africa before winter sets in |
Butterfly migration is not very common, but many readers may
have heard about the spectacular migration of the monarch butterfly in North
America. Not as spectacular, but nonetheless quite amazing, two of our native UK
butterflies migrate as well.
Painted ladies come to our shores in the thousands
in a good year, and they migrate back to Africa in autumn to escape the hostile
conditions of our North European winters. The Red admiral is also a migratory
species, and after spending the summer in the UK, a part of the population will
migrate back to continental Europe. However, thanks to global warming, an
increasing number of Red admiral individuals now stay in the southern counties
of the UK, where they hibernate in sheltered places.
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Many Red admiral`s migrate back to continental Europe |
We hope you enjoyed reading about the ingenious ways of
pollinators to survive our winters. Look out in spring for the lucky ones, the
pollinators which have survived winter, and celebrate a new year of bees,
butterflies, hoverflies and other pollinators buzzing and busily flying around
our flowers and crops.
Long may it continue ... .
A very interesting read, thanks. The other day, I was pulling up some leeks that I'd been growing inside looroll inserts to keep as much white as possible. One had a hibernating ladybird in and of course I had to leave it! It's the only leek left out there but now I'll let it flower :-)
ReplyDeleteThat`s nice that you let the ladybird alone. As soon as it gets warmer it will emerge and will start eating your aphids :-).
DeleteIt is often that when people do the big autumn tidy-up they unknowingly clear away lots of hibernation/shelter places for insects (sometimes inclusive the insects). Its best to leave everything until late winter or at least to be not too tidy in the garden.
You are lucky. I haven't seen a ladybird for three years - the last time I saw one was on a Budlea and there was only one single Ladybird then. Two years before that in Cardiff I saw quite a lot on a bush. When I was a kid there were so many of them and in so many different colours. O hate what we have done to this world as a species.
DeleteI hope against hope to see one this year. I've put houses out but so far have just a couple of Leaf Cutter Bees taking up the offer of a safe haven for the next generation.
Fine article and quite thorough. I didn't know about Bombus terrestris.
ReplyDeleteI have been pondering this issue myself. Here is what I gathered: "Pollinators and the Garden in Winter" http://nativeplantwildlifegarden.com/pollinators-and-the-garden-in-winter/ and "Hummingbrd Moths: Where do They go in Winter? http://pollinators.blogspot.com/2009/12/hummingbird-moths-where-do-they-go-in.html
Thank you for your comment and the links. Very interesting. I always wondered how the different insect pollinators survive our harsh winters so started researching about it. I find the different survival strategies quite amazing.
Deletewhat a lovely site.
ReplyDeleteUseful, interesting.
Do you have a list of pollinator-friendly plants grouped by season (I know the rhs has a good list but have seen plants listed on other reputable sites as pollinator-friendly which aren't on rhs site)?
We are trying to increase the number of wildlife-friendly plants in the garden of our (rented) suburban Dublin house (solid walls between plots so no chance of hedgehogs passing through alas.
We don`t have such a list yet but we are planning to compile one using our own data. 2 years of pollinator sampling have given us a pretty good idea of what plants pollinators prefer and what plants they don`t visit. But it will take a while as we are currently analysing the data. But in the mean-time you cannot really do something wrong if you avoid all the highly-bred cultivars (mostly with double flowers) and most bedding plants.
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ReplyDeletevickie lynn swayze
Your insightful blog on "Where do pollinators go in winter?" brilliantly explores the hidden world of these vital creatures. The curiosity you ignite is akin to the excitement of discovering new insights, perhaps even with the help of exclusive promotions and discounts through ''UsePromos.'' A journey that mirrors nature's mysteries and savvy exploration! #UsePromos
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ReplyDeleteGreat blog! I never realized how crucial it is to understand pollinators' winter habits. Your insights on their survival strategies and the importance of providing winter habitats are eye-opening. Thanks for raising awareness on this essential topic!
Loved this post! Absolutely awesome content!Veronica Dantas
ReplyDelete